In the long term evolution infrastructure, a UE can be in one of two radio resource control (RRC) states. These are LTE_IDLE and LTE_ACTIVE.
The UE can be configured for discontinuous reception (DRX) in both the LTE_IDLE and the LTE_ACTIVE states. DRX allows the UE to synchronize its listening period to a known paging cycle of the network. By synchronizing the listening period, the UE can turn off its radio transceiver during the standby, thereby significantly saving battery resources. As will be appreciated by those skilled in the art, unless a UE is used extensively, a large drain on its battery comes from the standby cycle in which it monitors the paging channel and measures serving and neighboring cells. DRX parameters allow the mobile to synchronize with the network and to know that it will not receive another signal until a specified time has elapsed.
Utilizing DRX in an IDLE state is performed in present UMTS systems and is done by the network signaling to the UE a DRX parameter and synchronizing the UE and the network. As will be appreciated, in IDLE mode the UE can change cells from one cell to the other. Thus utilizing a DRX parameter does not cause significant issues.
In an ACTIVE state however, various issues exist for turning off the receiver based on a DRX parameter. This includes the fact that only network controlled handover is allowed in the LTE_ACTIVE state. Also, other issues include efficient signaling of activation and deactivation of DRX, measurement requirements of network signals during the DRX, handling of missed handover opportunities, and issues dealing with the length of the DRX value in which entity in the network can request DRX activation and reconfiguring the DRX period.
In current systems, when short and long DRX is configured for non real time traffic and the traffic volume becomes very low, the eNB wants to put the UE which may be either in short DRX or actively listening to downlink common control channels into long DRX, for further battery saving if there is no uplink and downlink transmission. In current E-UTRA specifications, the eNB needs to deactivate short DRX using a RRC reconfiguration message at first and then issue a go-to-sleep MAC control element (CE). If traffic pattern changes, however, the eNB needs to activate short DRX by RRC again.